/*
 * 版权所有 (C) 2015 知启蒙(ZHIQIM) 保留所有权利。[遇见知启蒙，邂逅框架梦，本文采用木兰宽松许可证第2版]
 * 
 * https://zhiqim.org/project/zhiqim_kit/zhiqim_git.htm
 *
 * ZhiqimGit is licensed under Mulan PSL v2.
 * You can use this software according to the terms and conditions of the Mulan PSL v2.
 * You may obtain a copy of Mulan PSL v2 at:
 *          http://license.coscl.org.cn/MulanPSL2
 * THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
 * EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
 * MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
 * See the Mulan PSL v2 for more details.
 */
package org.zhiqim.git.objer.loader;

import java.io.IOException;
import java.util.zip.DataFormatException;

import org.zhiqim.git.GitConstants;
import org.zhiqim.git.objer.PackFile;
import org.zhiqim.git.util.GitBytes;

import org.zhiqim.kernel.util.Asserts;

/**
 * 增量包对象加载器
 *
 * @version v1.0.0 @author zouzhigang 2017-3-30 新建与整理
 */
abstract class DeltaPackedObjectLoader extends PackedObjectLoader implements GitConstants
{
    private final int deltaSize;

    DeltaPackedObjectLoader(PackFile pr, long dataOffset, long objectOffset, int deltaSz) throws IOException
    {
        super(pr, dataOffset, objectOffset);
        this.deltaSize = deltaSz;
    }
    
    /************************************************************************************************/
    //子类必须实现的方法
    /************************************************************************************************/

    /** 获取基础对象加载器 */
    protected abstract PackedObjectLoader getBaseLoader() throws IOException;
    
    /************************************************************************************************/
    //实现
    /************************************************************************************************/
    
    @Override
    protected void load() throws IOException
    {
        if (data != null)
            return;

        try
        {
            PackedObjectLoader baseLoader = getBaseLoader();
            baseLoader.load();
            
            data = GitBytes.merge(baseLoader.getData(), pack.decompress(dataOffset, deltaSize));
            type = baseLoader.getType();
            size = data.length;
        }
        catch (DataFormatException dfe)
        {
            throw Asserts.exception(dfe);
        }
    }

    @Override
    public long getRawSize()
    {
        return deltaSize;
    }
}
